Pueblo Grande Museum, City of Phoenix
This shows a reconstruction of life on a Hohokam platform mound in the Sonoran Desert in the 13th century A.D.

Ancient Native Baby Boom Reveals Lesson in Over-Population


The greatest baby booms in North American history occurred between 500 and 1300 A.D. among southwestern Native Americans. The population soared and then crashed eight centuries later.

"We can learn lessons from these people," says Tim Kohler, an anthropologist at Washington State University (WSU), who co-authored the paper with WSU researcher Kelsey Reese.

Researchers say the Neolithic Demographic Transition, when people began eating more grain and less meat, is responsible for the population increase and the eventual demise of the ancient Puebloans.

The population boom came at a time when the early features of civilization—including farming and food storage—were at their peak, the researchers report in this week's issue of the journal Proceedings of the National Academy of Sciences.

The study examined a century's worth of data on thousands of human remains found at hundreds of sites across the Four Corners region of the Southwest. Scientists then detailed chronology of the region's Neolithic Demographic Transition, in which stone tools reflect an agricultural transition from cutting meat to pounding grain.

"It's the first step toward all the trappings of civilization that we currently see," says Kohler.

This is Montezuma Valley in Colorado, a fertile area with high population growth in the distant past. (Tim Kohler, WSU)

Maize was grown in the region as early as 2000 B.C. By 400 B.C., Kohler says, the crop provided 80 percent of the region's calories.

Crude birth rates--the number of newborns per 1,000 people per year--were by then on the rise, mounting steadily until about 500 A.D.

The growth varied across the region.

People in the Sonoran Desert and Tonto Basin, in what is today Arizona, were more culturally advanced, with irrigation, ball courts, and eventually elevated platform mounds and compounds housing elite families.
Yet birth rates were higher among people to the North and East, in the San Juan Basin and northern San Juan regions of Northwest New Mexico and Southwest Colorado.

Kohler said that the Sonoran and Tonto people eventually would have had difficulty finding new farming opportunities for many children, since corn farming required irrigation. Water from canals also may have carried harmful protozoa, bacteria and viruses.

But groups to the Northeast would have been able to expand maize production into new areas as their populations grew.

Around 900 A.D., populations remained high but birth rates began to fluctuate.

Sites like Pueblo Bonito in northern New Mexico reached their maximum size in the early 1100s A.D. (Nate Crabtree Photography)

The mid-1100s saw one of the largest known droughts in the Southwest. The region likely hit its carrying capacity.

From the mid-1000s to 1280, by which time all the farmers had left, conflicts raged across the northern Southwest but birth rates remained high.

"They didn't slow down," says Kohler. "Birth rates were expanding right up to the depopulation. Why not limit growth? Maybe groups needed to be big to protect their villages and fields. "It was a trap, however."

The northern Southwest had as many as 40,000 people in the mid-1200s, but within 30 years it was empty, leaving a mystery.

Perhaps the population had grown too large to feed itself as the climate deteriorated. Then as people began to leave, that may have made it harder to maintain the social unity needed for defense and new infrastructure, says Kohler.

Whatever the reason, he says, the ancient Puebloans show that population growth has clear consequences.

You need to be logged in in order to post comments
Please use the log in option at the bottom of this page



bullbear's picture
Submitted by bullbear on
All the research and studies of the early People seem to only draw more questions rather than answers. The remnants tell us that those living in the southwest traversed the vast desert lands and reached the Pacific Ocean multiple times as shells are found in many archaeological sites in Arizona and outlying regions. Canal systems built and used by the Hohokam are still evident today and although it sustained them and they thrived agriculturally - when a drought hit, it had devastating effects. Families may have been driven apart to seek refuge from the unforgiving lack of rain. Pottery shards and petroglyphs provide glimpses into their environment and life that they held of great value whether it was the four-legged or winged. Jump to today -- Modern man has built gargantuan dams and although they store water that can sustain millions of people for years, we remain vulnerable because there are so many people dependent upon what they provide. We are in a drought once again. Story sound familiar? Very fascinating. I often wonder why more songs of distinction are not created that give credit and distinction to civilizations that lived life with so little in their ecosystem, yet their fire still burns and we thirst to know of their fate. Fascinating.

tresojos's picture
Submitted by tresojos on
I have heard that it was the development of agriculture that caused increased population growth in the "Fertile Crescent" (Tigris and Euphrates river valleys), and it has been growing ever since. Hunter/gatherer societies don't overpopulate their environment very easily, because their numbers are so directly connected with the supply of game. If humankind had never learned agriculture, we couldn't possibly have expanded to 7 billion on this planet. What is even more interesting is that hunter/gatherer societies are more egalitarian. With agriculture, people could specialize in certain tasks, and more hierarchy came into being.

Read more